Oh, the weather outside is frightful — so frightful, in fact, The Post turned to survival expert Shane Hobel, founder of the Hudson Valley’s Mountain Scout Survival School, for advice on making it through Winter Storm Juno.

Hobel — who teaches a class in Central Park dealing with urban emergency preparedness (the next of which is Feb. 21; mtnscoutsurvival.com for more info) — gave us his five most unexpected survival tips for when worse comes to worst.

Build a fort

If you have no heat, stay warm by acting like a 5-year-old. “Do you remember tearing apart your parents’ living room and using the couch cushions to make forts?” asks Hobel. “We already know the instinctive pattern of creating a safe shelter — so go back to your childlike instincts.” Once warm bodies are inside the compact fort, the temperature will rise.

Emulate the homeless

“Who are the masters of urban survival?” says Hobel. “It’s the homeless — the masters who do this every day.”

For example: “Throw a couple of pieces of cardboard on the sidewalk, stand on it, and you’d be surprised how warm you get. Then throw it in the trash before you get on the bus,” says Hobel. “In the woods, we do the same thing, standing on a couple of sticks just to get ourselves off the earth.”

Make some leftovers

In case of loss of power, cook food now and stow it away. “Clearly, things in the fridge may perish,” says Hobel. “Since it is cold, if you do have a terrace, take advantage of that. Just because the electricity goes out doesn’t necessarily mean the food has to go bad. Wrap it in plastic, put it in a safe location and [seal it] so there’s no moisture or exposure to allow the food to rot.

“Hey,” he adds, “leftovers are good, even when they’re cold!”

Chow down on snow

If you’re out of hydration options, use the very source of your trauma to save you — just make sure you have a filter. “The danger is there’s a lot of air pollution in the city,” he says. “But there are some wonderful camping filters. Scoop up the snow on the roof, melt it down, and filter it through. Just be mindful of the dangers involved in the environment, such as pesticides, heavy metals and other contaminants.”

Pull out the silk

In extreme weather conditions, cotton can make you sweat, which can both dehydrate you and bring on hypothermia. Battle this by putting on the nice stuff: “I have 100 percent-silk long underwear,” says Hobel.